This invention relates to electrical wiring ducts for a building and more particularly to an improved method and structure for forming electrical wiring ducts in a concrete building floor.
Buildings formed from concrete are often partially constructed before a final floor plan is selected. After the basic building structure is erected, such buildings are subdivided into spaces such as individual offices. Utility ducts for wiring and comfort conditioning are sometimes formed in poured concrete floors to facilitate supplying required utilities to each space into which the building is subsequently divided. One prior art method for forming utility ducts in a poured concrete floor is shown in U.S. Pat. No. 3,093,933 which issued June 18, 1963 to Slingluff and in U.S. Pat. No. 2,975,559 which issued Mar. 21, 1961 to Hedgren. These patents disclose a building floor structure having a metallic cellular subflooring which forms parallel cells or conduits for carrying electrical cables and for air handling. Electrical ducts also are located immediately above and perpendicular to the cellular subflooring. These ducts are spaced across the subflooring to provide a desired spacing for electrical service connections. Access fittings are attached to the ducts at desired locations and the ducts are connected to the appropriate subfloor cells. A concrete floor is then poured over the cellular subflooring to embed the electrical ducts. Wiring for power and communications is passed through the subflooring cells and the desired ducts for serving the floor area wherever such service is needed. By running electrical power and communications wiring through different subfloor cells and through alternate ducts, the power wiring is shielded in accordance with some building codes and the communication wiring is isolated from the power wiring to minimize induced electrical noise. However, a building floor structure of this type is unnecessarily expensive because of the high cost for the cellular metallic subflooring and of the need for using separate metal channels for forming both power and communications ducts in the floor.